The present invention relates to a tool for maintaining overhead valves in a raised closed position to permit a workman to remove and replace valve springs, tappets and other valve connections and effect adjustment and repairs to the valve super structure. The closest prior art known to the inventor and his attorney is an ordinary compressed air hose of the type used to inflate tires with a special fitting to permit the same to be connected to the spark plug opening to apply air pressure to the entire interior of an automotive cylinder above the piston and against the valve.
This prior method is effective in general but is subject to certain practical objections. Furthermore, a source of compressed air is not always available to the mechanic and there is a risk of disconnection of the same either at the compressor or at the spark plug opening itself. In any such case, a valve may, upon disconnection from the super-structure, fall into the cylinder and this will require entire disassembly of the cylinder head structure to recover the valve.
Applying relatively high compressed air pressure directly into the combustion chamber as is practiced in the prior art has the additional disadvantage and actual danger in that this air pressure sometimes rotates the engine by continuous pressure on the piston involved and may cause harm to a worker if he happens to be in close contact with the engine fan.